This invention relates to color television receivers and more particularly to circuitry responsive to changes in ambient light conditions to effect alterations in both contrast and color response of the color television receiver.
It is well known that picture quality of a television receiver varies as the ambient lighting conditions surrounding the television receiver vary. Thus, manual controls for both contrast affecting the luminance portion of a receiver signal and color affecting the chrominance portion of a receiver signal have long been available.
Also, automatic control of contrast and color responsive to variations in ambient lighting conditions is known. For example, one known automatic contrast and color control system for a color television receiver suggests a light responsive device disposed near the faceplate of a cathode ray tube and utilized to control both luminance and chrominance amplifiers of a color television. More specifically, the known circuitry employs an ambient light responsive device to effect amplification control of a chrominance signal channel and an optical isolator or light emitting diode in combination with a light dependent resistor to control the luminance signal channel of the receiver. Thus, isolation is achieved by independent light responsive devices.